class Solution {
public:
    int coinChange(vector<int>& coins, int amount) {
        const int INF = 0x3f3f3f3f; // 无穷大的一半
        int n = coins.size();
        vector<int> dp(amount + 1, INF);
        dp[0] = 0;
        for(int i = 1; i <= n; ++i)
        {
            for(int j = coins[i - 1]; j <= amount; ++j)
            {
                dp[j] = min(dp[j], dp[j - coins[i - 1]] + 1);
            }
        }
        return dp[amount] >= INF ? -1 : dp[amount];
    }
};